The present invention relates to an intake duct and process for influencing the flow rate in the duct. More particularly, it relates to an intake duct of an internal-combustion (IC) engine in which a gas flow is controlled by a valve and the duct has a defined flow profile by which the flow rate of the gas flow is continuously accelerated.
In a known flow duct such as shown in German Pat. No. DE-OS 35 08 763, the flow profile is configured such that it tapers continuously toward the valve seat insert. This configuration is based on the physical principle that, when the flow is unimpaired, the lowest losses occur in the flow duct if the cross-section of the flow duct narrows down continuously or the flow rate of the gas flow is increased continuously. In the case of a flow duct having a valve, however, an unimpaired flow cannot be realized inasmuch as the valve causes a considerable flow resistance. This resistance, in connection with a flow profile of this type, prevents optimized operation of the internal-combustion engine.
In addition, a known inlet duct shown in German Pat. No. DE-PS 28 22 058 which has a duct segment disposed downstream in front of the valve and configured to be circular, tapered, and leading into a cup constructed as a swirl inlet chamber. The cup is arranged asymmetrically with respect to the duct segment, and a sleeve is inserted into the segment adjacent to the valve. This construction has, on the one hand, the disadvantage that the sleeve will cause losses as a result of an impact in the flow direction. On the other hand, the boundary of the sleeve which is adjacent to the valve forms a breakaway edge which also causes flow losses. Additional flow losses occur in this construction as a result of the formation of turbulence in the cup.
It is an object of the present invention, therefore, to construct an intake duct in a cylinder head of an internal-combustion engine such that the flow rate of the gas flow takes into account the resistance caused by the inlet valve for achieving better operating characteristics of the internal-combustion engine, for example, as a result of an optimized volumetric efficiency.
This object is achieved in accordance with the present invention by configuring the intake duct downstream in the flow direction with a defined flow profile which, in a first intake duct segment, has a uniform cross-sectional contraction up to a cross-sectional transition area situated relatively closely in front of the valve stem and after that, in a second intake duct segment, has a widening uniform cross-section.
The principal advantages achieved with the present invention are that the gas flow in the intake duct segments of the cylinder head has an optimized flow rate course which accelerates the gas flow up to the cross-sectional transition area and then decelerates it. The deceleration causes a reduction of the flow resistance which improves the volumetric efficiency of the internal-combustion engine. This, in turn, has a performance-increasing and consumption-reducing effect.